ORGANIC MOLECULES IN AN ELECTRICAL CIRCUIT: AN AFM STUDY OF A NEGATIVE-DIFFERENTIAL-RESISTANCE MOLECULE

摘要

2,5-di(phenylethynyl)-4'-4"-dithiolate-1-nitrobenzene has been shown to exhibit negative differential resistance (NDR) and spontaneous switching when inserted into inert molecular monolayers between metal contacts. We have used conducting atomic force microscopy to measure the electronic properties of individual dithiolated molecules 2,5-di(phenylethynyl)-4'-4"-dithiolate-1-nitrobenzene and 2,5-di(phenylethynyl)-4'-4"-thioacetyl-benzene inserted into an alkanethiol monolayer and chemically bonded to gold nano-contacts to form a covalently-connected molecular circuit (bonded contacts). The data show qualitative agreement with previously published results for similar molecules deposited in a nanopore containing several hundred molecules, allowing us to make the important conclusion that the measured negative differential resistance (NDR) is native to the molecule and not an intermolecular phenomenon.